There’s a scene about halfway through the film in which Jake Gyllenhaal’s cop character goes into a spooky house looking for a killer. He goes into a room full of locked trunks, and opens them to reveal… snakes. Who are alive. And slither all over the room.

Why are the snakes there? Why are they kept in locked trunks, as opposed to, you know, cages? Is there any reason for them to be there, other than to look scary when a cop opens them?

And that’s the problem here. “Prisoners,” directed by French-Canadian auteur Denis Villeneuve, starts off as a tense, well-acted thriller with an intriguing premise. But it gets so silly as it goes along, with seemingly limitless red herrings, that the only reason to keep watching is to wait for the payoff, which is extremely lackluster.

There are three things very wrong with “Prisoners”: It’s insanely long at 150 minutes, the longer it goes the more ridiculous and contrived its plot gets, and it steals most of its best ideas from better movies like “Seven,” “Mystic River” and Zodiac

The plot sounds like it was based on a Dennis Lehane novel that doesn’t exist: On Thanksgiving night, in an unnamed, rural Pennsylvania town, the young daughters of Hugh Jackman and Terrence Howard mysteriously disappear. A mentally-handicapped adult in a nearby trailer (Paul Dano) comes under suspicion, but there’s no hard evidence. Meanwhile, there’s rumblings about past kidnappings that sound an awful lot like this one, another creepy suspect emerges, and the two fathers must question how far they can go to free their missing daughters.

Gyllenhaal is the detective on the case, because rather than a nationwide manhunt that’s covered on national TV and looked into by dozens of law enforcement officials, the disappearance and possible murder of two young girls is for some reason investigated by only one local cop. Though at least, unlike in “Zodiac,” Gyllenhaal’s character isn’t a moonlighting cartoonist.

The acting is pretty strong throughout, to the point where one wishes it were serving a better movie. Jackman’s work, in particular, is heartbreaking, although Bello, a fine actress, is driven so catatonic by her daughter’s kidnapping that she barely registers as a character at all, and is off-screen for the majority of the film.

There are various other missteps. The killer’s motive is explained with one, extremely hazy line of dialogue, which is a huge letdown. This is also one of those movies that occasionally tosses in references to Catholicism, whenever it feels like injecting some unearned gravitas. There’s some ridiculousness involving mazes and secret maps. And Dano’s character, for some reason, is Alex Jones, making him America’s second-scariest, second-most insane Alex Jones.

It’s a shame though, as the film looks fantastic throughout and is fantastically shot by the great Roger Deakins. But that and the acting can’t overcome that silly, ludicrous plot. That “Prisoners” was a critically acclaimed festival hit that’s actually getting Oscar attention is mystifying to me.